Separation and filtration of microparticles based on size may be important for many applications such as biochemical and environmental assays, micro/nano-manufacturing, and clinical analysis. Traditional methods for separation and removal of microparticles from solutions involve the use of a membrane filter, which are typically limited by the membrane pore size, making them inefficient for separating a wide range of particles. Clogging and high costs associated with membrane-based filtration on the microscale have resulted in the development of a number of membrane-less separation techniques. Sedimentation, field-flow fractionation (FFF), hydrodynamic chromatography (HDC), pinched flow fractionation (PFF), electrophoresis, dielectrophoresis, acoustic separation, diffusion-based extraction, deterministic lateral displacement, centrifugation, and inertial focusing are some of the techniques recently demonstrated for separation and concentration of particles and biological molecules.
However, microscale membrane-less separation techniques are not an attractive choice for filtering and separating particles in large sample volumes (˜mL) due to long analysis times. In addition, the external force fields required for their functionality can potentially damage biological macromolecules and cells, and the active sources needed to produce these fields for particle manipulation often make the device fabrication complex and difficult to integrate with conventional LOC components. Finally, dependence on particle charge and mobility presents constraints on the type of particles that can be analyzed. Regarding passive membrane-less microfluidic devices, due to their small diffusion coefficients, large particles such as cells cannot be filtered efficiently as diffusion times and lengths become impractically long for most LOC applications.
Accordingly, alternative particle separator devices capable of continuous and complete separation of particles at low pressure drops and high throughputs are desired.